Field of the Invention
This invention relates to the field of wireless communication systems.
Background to the Invention
The following abbreviations are being used in the specification:
DECT Digitally enhanced cordless telecommunication
ULE Ultra low energy
NEMo No Emission Mode
PM Packet Mode transfer
Today a ULE base station must repetitively transmit a beacon known as a ULE dummy bearer, which allows any ULE device to lock fast, using the information that is contained in a ULE dummy bearer BField of the ULE dummy bearer.
This requirement to have repetitive ULE dummy contradicts with NEMo operation, where the base station is supposed to switch off any transmitter for a long time, in order to be environmental or health friendly.
This makes it necessary today, to disable NEMo if ULE devices are enabled in the base station (thereby allowing the base station to communicate with ULE devices). The disabling of NEMo mode is often not acceptable to customers.
In order to achieve the low power demands a ULE device will spend the majority of its time in a “deep sleep” state, from which it will awake periodically or when triggered, to communicate with the base-station.
ULE
There are 2 main aspects which minimize the power consumption of the ULE device: (a) ULE device will gain sync (fast sync) with the base-station very quickly and (b) the communication between a ULE device and the base station is very short.
Fast Sync involves:                a. The base station entertains a permanent ULE dummy bearer (it repetitively transmits the ULE dummy bearer).        b. The ULE dummy bearer has a special sync word so that only ULE devices will lock to it very quickly.        c. The ULE dummy bearer has a “Sync Subfield” which allows the ULE device to lock to it very quickly (no need to wait and collect Qt/Pt information from several frames). This allows the ULE device to synchronize.        d. The ULE device will have remembered where it found the ULE dummy bearer last time, assuming the base station hasn't changed the carrier. This means the ULE device most of the time does not have to scan all 10 carriers.        
The communication between ULE device and base station is very short—“Packet Mode” and a ULE device can start packet-mode communication on any “free” slot of the base station. In order to save current and time of the ULE device the base station may perform RSSI scanning on the “free” slots and send the quiet slots information to ULE device on extended dummy information included in the ULE dummy bearer.
Communication with the ULE device is generally implemented by a short exchange of packets.
NEMo                a. Both NEMo handset and base station know whether the other one can do NEMo.        b. NEMo is initiated from the base, but only if all handsets have indicated to support it during registration.        c. Base station transmits (pages) the fact that it soon will enter NEMo. This is a countdown mechanism. If any NEMo handset doesn't like that, it can setup a link. The NEMo handset would setup a link only when there is a call requested.        d. Once the countdown ends the base station stops all transmissions. The base station and the NEMo handsets perform NEMo scanning in order to detect transmissions from each other.        e. The base station continuously scans. A NEMo handset scans each 1.28 seconds (N210/2).        f. When the base station wants to wake up the NEMo handset (always all the NEMo handsets will be woken), the base station transmits a NEMo Dummy bearer, and optional additional DummyPointer bearers for 2.56 s (N210).        g. When a NEMo handset sees them, it wakes up, quickly synchronizes all counters, and sets up a DummyRequest bearer.        h. When the NEMo handset wants to wake up the base station, it transmits a DummyRequest bearer for 16 frames (N211), and falls back to immediate NEMo scanning.        i. When the base station “sees” the DummyRequest bearer and establishes a NEMoDummy bearer (same as base station imitated wakeup).        j. NEMo devices today are typically operating on a fixed preferred carrier (Q12.a23=0).        
There is a growing need to reduce the emission of a base station while supporting ultra low energy (ULE) devices and NEMo devices.